Include malloc.h if system has it.

src/shmem.h

@@ -28,7 +28,9 @@ extern "C" {
 #if CAVE
 	/* Shared memory definitions */
 
-#include <malloc.h>	/* for amalloc() */
+#ifdef HAVE_MALLOC_H
+# include <malloc.h>	/* for amalloc() */
+#endif
 
 #define NewN(type, count)     (type *)shmalloc((count) * sizeof(type))
 #define RenewN(p,type,count)  (type *)shmrealloc(p, (count) * sizeof(type))